Damping technology reduces bouncing of concrete flooring slabs Tuesday, 19 July 2016

Civil engineers from Swinburne's Centre for Sustainable Infrastructure have developed a floor vibration damping technology that reduces the "bouncing" of thin concrete flooring slabs in buildings.

Modern office buildings are typically constructed with thinner concrete flooring slabs, with longer unsupported spans, in order to accommodate the growing trend for open plan offices. However, these longer spans tend to "bounce" under the weight of people walking across the floor, which can be disruptive for workers.

Floor movements of as little as a tenth of a millimetre can cause significant discomfort to workers seated at desks. Buildings around the world are now governed by design guidelines that specify the maximum permissible foot traffic vibration limits.

To solve this problem, civil engineers Professors Emad Gad, John Wilson and colleagues from Swinburne’s Centre for Sustainable Infrastructure developed a floor vibration damping technology called the tuned mass damper (TMD) that is both compact and cost efficient, allowing it to be retrofitted into existing offices.

This tuned mass damper is significant because conventional vibration reduction measures required increasing the stiffness of the floor with structural beams, and damping the vibrations with added weight — measures that could only be implemented during construction, with little avenue for retrofitting into a working office environment.

The new damping technology has already been retrofitted in buildings in Australia and the UK.

“Modern open-plan, ‘electronic’ offices tend to be long span, lightweight and with little furniture,” says Gad.

“Floors that suffer excessive vibration due to people walking can be rendered unusable, even though they are perfectly safe. Until now, there was no proven technology that could be economically and efficiently applied to fix such problems.”

The TMD consists of multiple flat beams of viscoelastic rubber sandwiched between steel plates, each is fixed at one end and weighed down with a steel plate at the other. It requires no electrical power and is simple and cheap to construct. It is less than 15 cm high, so easy to install in the standard sub-floor gap found in most offices.

By matching the resonant frequency of the TMD to that of the measured floor vibration, the TMD system has been demonstrated to reduce the peak acceleration of vibration by more than 50 per cent, bringing the vibration down to levels below the threshold of discomfort.

[Image: FreeImages.com/Seda Inal]